|Dimensions||2626μm x 2626μm|
|Power||999 mW @ 1.2 V, 400 MHz|
For the PULP project we use an optimized RISC-V core that we call RI5CY. This core has been optimized for energy efficiency in data processing applications. While it is very energy efficient (it does more per pJ) it is not very small (around 40 kGE) and in cases where there is a very light load like in control applications it also consumes more power. Many people have been asking us for a smaller core, and we set ourselves the goal to have a 10kGE RISC-V core. We ended up with two different small cores, one with a 3 stage pipeline (ZeroRISC) and another one with a single cycle architecture.
We have a strong interest in Cryptographic Hardware and a long standing relationship with IAIK of TU-Graz. One of the cores (Remus) in Patronus has been designed to withstand fault attacks by adding Control Flow Integrity (CFI). For this core we also added support for the Priviledged Mode version 1.9 of RISC-V, a small MMU. We have also made a port of the sel4 operating system to run with this configuration.
In total there are three cores in the system:
All cores have access to the same 640 kByte memory, organized in 4 banks and accessed for both data and instructions through a logarithmic interconnect. In addition to the SRAMs, there is a small (6 kBytes) custom macro with standard cell based memories. All cores have access to a set of interfaces including a standardized camera interface
Patronus is essentially a single core PULPino line of chip (although there are three different cores in it). So it continues the tradition carried over from Imperio to name the single core implementations from the Harry Potter Universe. Since one of the cores features a protection against fault attacks, the chip is called patronus, a defensive spell which produces a guardian animal. In the books, it is Remus Lupin that has a Wolf patronus. However, here the wolf logo on the chip foreshadows the next PULP design Mr. Wolf (because Mr. Wolf solves problems). There is also a small text that says 640 Kbytes ought to be enough for everybody, a quote commonly attributed to Bill Gates (but probably is not correct). Patronus has 640 Kbytes of SRAM (and a bit more).